This invention relates to pacemaker apparatus and a method for programming a pacemaker and in particular an apparatus and method of direct decimal programming of pacemaker rate.
The desirability of programmable pacemakers has become a clinical and commercial reality, and is well documented in the literature. There are a number of reasons why it is advantageous to be able, at any time after implantation, to change operating parameters of the pacer so as to provide more optimum operation in response to the observed condition of the patient. Presently available pacemakers provide for programming of a large number of different pacer parameters, in different combinations. However, the pacer parameter, or variable which is most widely programmed for patient treatment is that of pacing rate, i.e., the rate of delivering stimulus beats from the pacemaker to the patient's heart.
Reference is made to U.S. Pat. No. 4,124,031, issued Nov. 7, 1978, PROGRAMMABLE PACER, assigned to the same assignee. In this patent, at columns 1 and 2, there is presented a discussion concerning the desirability of having a pacing system which utilizes the most simple and reliable programming means available, namely a simple magnet. As stated in the referenced patent, an implanted pacemaker which is programmable with a simple magnet provides the patient with the most in inherently reliable means of communicating with the pacemaker, due to the virtual universal availability of simple magnets. Also, as disclosed in the referenced patent, such a pacing system programmable with a simple magnet may be made as secure as any more complex pacer in terms of avoidance of unwanted interference or spurious signals.
Having achieved the optimum system for programming the pacemaker in terms of overall lifetime reliability, a next design objective becomes that of providing a technique, or method of programming which is inherently simple for the physician to utilize, and which also can be performed very quickly. Many present day programmable pacer models require the use of a complex transmitter in order to properly program the pacemaker. Although such transmitters enable effective "pushbutton" programming, which has a certain gadget appeal, it is necessary for the physician to properly initialize the programmer/transmitter by ensuring that it has power, setting the dials properly, positioning it accurately, etc. Even then, having thrown the proper switch or pushed the proper button, the physician has no feel or sense that the programming has been achieved properly, and must follow the standard test procedures to determine that indeed the desired program has been received.
By contrast with the more complex programming arrangements, the essence of the subject invention is to provide a simple programming arrangement to which the physician can readily relate, for programming the pacemaker rate. What is provided is a simple programming code which permits the doctor to directly program and count the programmed rate as it is being entered, so that the doctor has a sense of direct control over the procedure. The pacemaker and method of this invention employs direct decimal programming, meaning that the doctor first directly enters a program signal corresponding to the decade count of the desired heart rate, and then enters a program corresponding to the units count of the heart rate. For both the decade and units programming steps, the doctor simply places the magnet over the patient's chest in the vicinity of the pacemaker and removes it a number of times corresponding to the decade and/or units count desired. By way of example, if a doctor desires to program a new rate of 75 beats per minute, he first applies the magnet (i.e., positions it in the vicinity of the patient's pacemaker so that the magnetic field thus created can be sensed within the pacemaker) and then removes it 7 times, corresponding to 7 decades or 70 beats per minute. The doctor then holds the magnet in an applied position for a predetermined minimum period, and then repeats the procedure, applying the magnet and removing it 5 times in order to introduce the desired units count. The pacemaker thereafter automatically adjusts the pacing rate according to the two inputs, providing a rate in this example of 75 bpm.
It is immediately seen that this technique of direct decimal programming is simple and easily understood, and is one which enables the physician to directly count the programmed rate as he is entering it. The "program language" that is employed is a universal language, since the decimal system is utilized universally. All physicians who deal with pacing in whatever geographical location, count heart rate in terms of bpm as expressed in decimal terms. Accordingly, the most natural and direct way of programming this parameter is to first introduce the decades, or tens count, and then introduce the units count. It is thus seen that the technique of direct decimal programming employs a natural language which the doctor immediately grasps, and which importantly provides the doctor with a means of having a sense of control over the process of programming the pacer rate. The programming method is direct, i.e., the doctor puts the program directly into the pacemaker without any intervening mechanism; it is also quick, simple and reliable.